This invention relates to evaluating neuromuscular blockade by monitoring a thumb twitch response to train-of-four (TOF) nerve stimulation.
The use of muscle relaxants is an integral part of anesthetic management in present day practice. Currently, neuromuscular blockade is evaluated by determining the muscular reaction to train-of-four (TOF) nerve stimulation. There is equipment available for mechanical measurement of muscular response, such as the use of EMG, force displacement transducers, and most recently, the use of an acceleration transducer-based system of neuromuscular monitoring. These types of equipment, however, take time to set up and adjust, and are expensive. Because of these limitations, the daily routine use of such mechanical monitoring equipment is impractical. The evaluation of neuromuscular blockade therefore, at present, relies on the response, such as thumb twitch, to the TOF nerve stimulation which is evaluated either visually or manually (tactile).
Tactile or visual evaluation of neuromuscular blockade is subjective and involves uncertainty especially in the recovery phase. Furthermore, in certain surgical procedures when both hands are inaccessible, evaluation of the TOF by ulnar nerve stimulation is difficult or impossible. In such situations, muscle relaxants are given without clear objective criteria.
Accordingly, there is a need to provide a simple and inexpensive way of measuring the thumb twitch response to TOF stimulation during anesthesia.
An object of the present invention is to fulfill the need referred to above. This objective is obtained by providing a simple method for monitoring of the thumb twitch. The method uses an apparatus having a support structure configured for supporting at least a hand of a patient. The apparatus includes a pressurized biasing member operatively associated with the support structure and located to contact the patient""s thumb when the patient""s hand is placed in the support structure. A sensor is associated with the biasing member. The method includes placing the patient""s hand in the support structure such that the thumb of the patient contacts the biasing member with the biasing member being disposed between the thumb and the support structure. The ulnar nerve is stimulated to cause the thumb to adduct and press the biasing member against the support structure with the sensor generating an electrical signal in response to the pressure exerted by the biasing member. The electrical signal is monitored.
In accordance with another aspect of the invention, an apparatus for monitoring thumb twitch includes a support structure constructed and arranged to support at least a hand of a patient. A pressurized biasing member is operatively associated with the support structure and located to contact the patient""s thumb with the biasing member disposed between the thumb and support structure when the patient""s hand is placed in the support structure. A pressure sensor is associated with the biasing member to generate an electrical signal corresponding to pressure exerted by the biasing member.
Other objects, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification.